The present invention relates to a specimen holder, a specimen preparation device, and a positioning method.
A specimen preparation device which utilizes an ion beam (ion beam processing device) is known as a device for preparing an observation-analysis target specimen using an electron microscope, an electron probe microanalyser (EPMA), an Auger microprobe, or the like (see JP-A-2013-137995, for example).
When processing the surface of the specimen by applying an ion beam to the surface of the specimen at an incident angle close to 90° using such a specimen preparation device, the specimen is normally positioned using an optical microscope.
FIG. 21 is a view schematically illustrating the state of a specimen 2, when processing the specimen 2 by applying an ion beam to a specimen surface 4 of the specimen 2 at an incident angle theta close to 90°. Note that the arrow illustrated in FIG. 21 represents an axis which corresponds to the optical axis of the ion beam (or the optical axis of the optical microscope).
Since the depth of focus of an optical microscope is shallow, the in-focus range on the tilted specimen surface 4 illustrated in FIG. 21 is narrow. Therefore, it is difficult to cause the ion beam application position to coincide with the target on the tilted specimen surface 4 using an optical microscope. Thus, the specimen is positioned as described below, for example.
FIGS. 22A to 22D are views illustrating an example of a known specimen positioning method that positions the specimen 2. Note that the intersection of the dash-dotted lines illustrated in FIGS. 22A to 22D represents the axis of tilt of the specimen. The ion beam application position is situated on the axis of tilt.
As illustrated in FIG. 22A, the specimen surface 4 of the specimen 2 is placed perpendicular to the optical axis of the optical microscope, so that the target on the specimen surface 4 can be easily observed using the optical microscope.
As illustrated in FIG. 22B, the position of the specimen 2 is adjusted in the height direction so that the specimen surface 4 coincides with the axis of tilt.
As illustrated in FIG. 22C, the target on the specimen surface 4 is moved to coincide with the ion beam application position using the optical microscope.
As illustrated in FIG. 22D, the specimen 2 is tilted at the tilt angle used when processing the specimen 2 by applying the ion beam. In this case, since the target on the specimen surface 4 is situated on the axis of tilt, the target does not move when the specimen 2 is tilted. Note that the arrow illustrated in FIG. 22D represents the ion beam.
The specimen can be positioned by performing the above steps.
According to the above specimen positioning method, however, it is necessary to cause the specimen surface 4 to coincide with the axis of tilt of the specimen (see FIG. 22B). Therefore, it is necessary to provide a mechanism which accurately adjusts the height of the specimen 2 in the specimen stage. Moreover, even when the target on the specimen surface 4 is moved to coincide with the ion beam application position (see FIG. 22C), the position of the target may be shifted when the specimen 2 is tilted (see FIG. 22D) depending on the accuracy of the specimen tilt mechanism.
Specifically, it is difficult to accurately position the specimen using the above specimen positioning method.